A complex of 45- and 47- kDa proteins was identified from Mycobacterium bovis BCG culture filtrate as an immunodominant target for antibody response after immunization with living BCG. The complex was further purified from the filtrate by chromatographic methods. Carbohydrates were identified to be attached to the molecules by a lectin blotting assay and `-mannosidase digestion. We used mass spectrometry to determine the MWs of the component proteins and the digested products and to provide information on nature of the glycosylation.